/Engine/Source/Developer/SkeletalMeshUtilitiesCommon/Public/LODUtilities.h
Build the vertex attributes
static bool UpdateLODInfoVertexAttributes ( [USkeletalMesh](API\Runtime\Engine\Engine\USkeletalMesh) * InSkeletalMesh, int32 InSourceLODIndex, int32 InTargetLODIndex, bool bInCopyAttributeValues )